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usleep.c revision 1.2 
      1 /*
      2  * Copyright (c) 1989 The Regents of the University of California.
      3  * All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  * 1. Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  * 2. Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in the
     12  *    documentation and/or other materials provided with the distribution.
     13  * 3. All advertising materials mentioning features or use of this software
     14  *    must display the following acknowledgement:
     15  *	This product includes software developed by the University of
     16  *	California, Berkeley and its contributors.
     17  * 4. Neither the name of the University nor the names of its contributors
     18  *    may be used to endorse or promote products derived from this software
     19  *    without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     31  * SUCH DAMAGE.
     32  */
     33 
     34 #if defined(LIBC_SCCS) && !defined(lint)
     35 /*static char sccsid[] = "from: @(#)usleep.c	5.6 (Berkeley) 2/23/91";*/
     36 static char rcsid[] = "$Id: usleep.c,v 1.2 1993/07/30 08:23:58 mycroft Exp $";
     37 #endif /* LIBC_SCCS and not lint */
     38 
     39 #include <sys/time.h>
     40 #include <sys/signal.h>
     41 #include <unistd.h>
     42 
     43 #define	TICK	10000		/* system clock resolution in microseconds */
     44 #define	USPS	1000000		/* number of microseconds in a second */
     45 
     46 #define	setvec(vec, a) \
     47 	vec.sv_handler = a; vec.sv_mask = vec.sv_onstack = 0
     48 
     49 static int ringring;
     50 
     51 void
     52 usleep(useconds)
     53 	unsigned int useconds;
     54 {
     55 	register struct itimerval *itp;
     56 	struct itimerval itv, oitv;
     57 	struct sigvec vec, ovec;
     58 	long omask;
     59 	static void sleephandler();
     60 
     61 	itp = &itv;
     62 	if (!useconds)
     63 		return;
     64 	timerclear(&itp->it_interval);
     65 	timerclear(&itp->it_value);
     66 	if (setitimer(ITIMER_REAL, itp, &oitv) < 0)
     67 		return;
     68 	itp->it_value.tv_sec = useconds / USPS;
     69 	itp->it_value.tv_usec = useconds % USPS;
     70 	if (timerisset(&oitv.it_value)) {
     71 		if (timercmp(&oitv.it_value, &itp->it_value, >)) {
     72 			oitv.it_value.tv_sec -= itp->it_value.tv_sec;
     73 			oitv.it_value.tv_usec -= itp->it_value.tv_usec;
     74 			if (oitv.it_value.tv_usec < 0) {
     75 				oitv.it_value.tv_usec += USPS;
     76 				oitv.it_value.tv_sec--;
     77 			}
     78 		} else {
     79 			itp->it_value = oitv.it_value;
     80 			oitv.it_value.tv_sec = 0;
     81 			oitv.it_value.tv_usec = 2 * TICK;
     82 		}
     83 	}
     84 	setvec(vec, sleephandler);
     85 	(void) sigvec(SIGALRM, &vec, &ovec);
     86 	omask = sigblock(sigmask(SIGALRM));
     87 	ringring = 0;
     88 	(void) setitimer(ITIMER_REAL, itp, (struct itimerval *)0);
     89 	while (!ringring)
     90 		sigpause(omask &~ sigmask(SIGALRM));
     91 	(void) sigvec(SIGALRM, &ovec, (struct sigvec *)0);
     92 	(void) sigsetmask(omask);
     93 	(void) setitimer(ITIMER_REAL, &oitv, (struct itimerval *)0);
     94 }
     95 
     96 static void
     97 sleephandler()
     98 {
     99 	ringring = 1;
    100 }
    101